Objective:To investigate the risk factors for nosocomial infection in older adult inpatients in some psychiatric hospitals in Ningbo of Zhejiang Province.Methods:The clinical data of 832 inpatients who received treatment in Ningbo Kangning Hospital and the Third Branch of Healthcare Group of Xiangshan Hospital of Traditional Chinese Medicine were retrospectively analyzed. These patients were divided into one infection group ( n = 45) and one non-infection group ( n = 787). The risk factors for nosocomial infection were analyzed. Results:Univariate analysis results showed that there were significant differences in age, disease type, primary pulmonary infection, time of antibiotics use, length of hospital stay, suffering from mental diseases, and use of urinary catheters ( χ2 = 10.721, 18.127, 12.183, 67.127, 56.326, 65.114, 27.153, all P < 0.001). Multivariate analysis showed that age ≥ 75 years, disease type, primary pulmonary infection, time of antibiotics use, length of hospital stay, suffering from mental diseases, and use of urinary catheter were independent risk factors for nosocomial infection in older adult inpatients ( OR = 3.360, 3.777, 5.238, 3.364, 3.939, 4.428, all P < 0.001). Conclusion:Age ≥ 75 years, disease type, primary pulmonary infection, time of antibiotics use, length of hospital stay, suffering from mental diseases, and use of urinary catheters are independent risk factors for nosocomial infection in older adult inpatients in some psychiatric hospitals in Ningbo of Zhejiang Province.